The man who discovered the bodies of his sister and niece says he is reliving "hell" after finding out today that Mark Lundy has been granted an appeal by the Privy Council.

Lundy was sentenced to life imprisonment with a minimum non-parole period of 20 years after he was found guilty of murdering his wife Christine and their seven-year-old daughter Amber in Palmerston North in 2000.

He has always maintained his innocence and his lawyers filed papers with the Privy Council in London in November.

The Privy Council confirmed this morning that it would grant Lundy permission to appeal.

The three-day hearing will begin in London on June 17.

Brother of Christine Lundy, Glenn Weggery, said he was not aware Lundy's appeal had been granted until the Manawatu Standard contacted him this morning.

"Bloody marvellous," he said.

"I'm never surprised by anything. I just want it to be over.

"They have been talking about this for so many years, it just puts all the rest of us through hell every time it's brought up.

"We're all trying to move on with our lives and let Christine and Amber rest in peace, but that just can't happen."

When asked if he had considered Lundy's conviction may be quashed, Weggery said he "didn't even really want to think about it".

"In my mind, he's guilty as," he said.

Weggery said he would love to travel to London to be at Lundy's hearing and "put his two cents in", but he couldn't afford to.

Speaking to RadioLive this morning, Lundy's lawyer David Hislop QC said he was "delighted".

"We've put a lot of hard work into this, and we want to see that Mark gets the very best opportunity that he can to put his story across," he said.

Hislop said the basis of the appeal included a number of factors, but the main one was the science that was deployed to identify the brain tissue found on Lundy's shirt.

Hislop said the science put forward in the trial by the Texan researcher was just an experiment.

"He had never done it before, the scientific world had never done it before. We say he's got it wrong," he said.

The Privy Council's judicial committee decision announcement said Lundy's appeal was on the basis that the jury's verdict should be set aside because it was "unreasonable" or "could not be supported having regard to the evidence in the case".

Lundy's previous legal team of Wellington lawyer Christopher Stevenson and Keith Becker, now based in Sydney, were to have appealed on the basis of discrediting brain or spinal tissue found on one of Lundy's shirts during the police investigation.

Hislop said he had not yet had a chance to speak with Lundy about the appeal decision, but that he was not surprised.

"Yes we did expect it, we wouldn't have filed otherwise," he said.

The next issue was how to raise money to get the scientists needed for the case from New Zealand to London, he said.

Hislop said the appeal was a "hybrid between a trial and an appeal" - evidence would be called and each party would have an opportunity to cross-examine.

"We won't have a lot of time, it'll be pushed through quickly," he told RadioLive.

Should the appeal be successful, the case could have a similar outcome to the David Bain case, he said.

"The Crown will make up their own minds if they want to retry Mr Lundy."

As the appeal has been granted, the Privy Council law lords can now consider Lundy's convictions, either upholding or quashing them, in which case the solicitor-general could order a retrial.

Given the high profile of the case, Ben Wilson, head of communications the Supreme Court of the United Kingdom, said the court would look at making arrangements to live-stream the hearing.

It is understood the legal bid was funded by supporters of Lundy involved in the Factual (For Amber and Christine - Truth Uncovered about Lundys) website.